Coverings for architectural openings, such as windows, doors, archways, and the like, have taken numerous forms for many years. Some coverings include a shade member that is extendable and retractable across an architectural opening. To retain the shade member in a desired position, some coverings include one or more counterbalance devices, such as one or more springs and/or drive mechanisms, that resist extension of the shade member.
Commercially-available counterbalance devices typically are provided with standard torque ratings, such as the holding torque of an electric motor or a torque output of a torsion spring. The weight of a shade member and a rail attached to the shade member often do not match the torque rating of commercially-available counterbalance devices. Manufacturers sometimes use a commercially-available counterbalance device with a torque rating that is stronger than the holding torque requirements of the covering, but this approach typically is relatively expensive and results in a spring or drive mechanism that is stronger than required. Manufacturers sometimes use a commercially-available counterbalance device with a torque rating that is weaker than the holding torque requirement of the covering, but this approach may not be effective because the torque of the counterbalance device is generally insufficient to restrain the shade member in a desired position without slippage. Manufacturers sometimes use a custom counterbalance device having the particular torque rating needed for each different covering, but this approach is expensive and generally not economical for mass production.